Medical connections are widely used in fluid delivery systems such as those used in connection with intravenous fluid lines, blood access, hemodialysis, peritoneal dialysis, enteral feeding, drug vial access, etc. Many prior art aseptic medical connections has been to puncture an elastomeric diaphragm or septum, which has one side in contact with the fluid, with a sharpened hollow hypodermic needle. The use of such hypodermic needles has been gradually decreasing as a result of both safety and cost considerations associated with infectious disease acquired from needle sticks. These connectors have been replaced with luer activated connectors which don't require hypodermic needles, but instead use an activator such as a luer on the end of a syringe or IV line to create a fluid path though a valve in a connector. The removal of the connector causes the valve to close when the line is disconnected. Such a system is described in U.S. Pat. No. 5,569,235 to Ross et al.
Typical connectors and valves of this type, such as described by Ross, have many attributes that are not ideal in medical applications for fluid delivery. First, such devices can have large priming volumes, that is the connector can have a large chamber associated with the valve element that must be filled with the fluid being delivered before that fluid is actually delivered into the patient line and the patient. For very low flow rates (for example, 0.1 milliliter per hour or 0.05 milliliters per hour), as is common for neonatal or infant care as well as other types of care, such a large priming volume can cause a delay of as much as several hours before the intended therapy reaches the patient. A connector having a low priming volume would allow an introduced therapy to reach the patient more quickly, even at low flow rates.
Second, fluid displacement can occur whenever a connection is made between two closed fluid systems. When a connection, such as a luer or hypodermic needle, is inserted into an intravenous connector or fluid tubing, fluid displacement occurs. Because the intravenous fluid is incompressible, a volume of fluid equal to the luer or needle volume is displaced out of the intravenous tubing and into the patient's blood vessel. This displacement of fluid from the intravenous tubing into the patient's blood vessel is referred to as antegrade flow. Similarly, when the connection is withdrawn, an equivalent volume of blood will be drawn back, usually through the catheter, into the intravenous tubing. This retrograde flow can be harmful when the blood drawn into the end of the catheter remains stagnant for a long period of time. The stagnant blood tends to settle, and may begin to clot, thereby restricting flow through the catheter and possibly requiring insertion of a new intravenous catheter into the patient. Connector systems providing for negative, or retrograde, displacement on insertion and positive, or antegrade flow on removal, are much more desirable in medical applications.
Third, most connectors use a septum, or permeable membrane at the connection site. These membranes must be penetrated on the insertion of the connector and therefore promote bacteria growth inside the connector. This septum is also susceptible to leaking when there is back pressure in the system. Connector systems that have swabable surfaces to allow for cleaning and which prevent leakage under backpressure are preferable.